The invention provides an
erdosteine purifying method. The method comprises the following steps: 1) preparing an
aqueous solution of crude
erdosteine: dissolving crude
erdosteine in an
aqueous solution which is near-neutral to alkaline, adding an
organic solvent capable of being layered with water for extraction to obtain the
aqueous solution of crude erdosteine, wherein the volume ratio of the
organic solvent to the alkaline aqueous solution is 0.05-20:1; 2) preparing fine erdosteine: regulating the aqueous solution of the crude erdosteine obtained in step 1) to be acidic by acid, separatingout solids, and performing filtering and
drying to obtain the fine erdosteine. On the basis of the specificity that the erdosteine structure contains carboxyl groups,
column chromatography which is high in operation difficulty and not suitable for industrial production is not needed for purification, only an alkali-solution and acid-isolation method is adopted for purification, operation is convenient in the purifying process, impurities in the crude erdosteine can be removed effectively, finally, purity of the fine erdosteine can reach 99.4% or higher, any individual
impurity is lower than 0.1%, yield is high, and the method is applicable to industrial production.